The metallization of semiconductors using an electrodeposition strategy is undergoing a tremendous renewal of interest, fueled by the recent success in utilizing copper interconnects in microchip fabrication. Copper is well suited as a replacement for the currently used aluminum principally due to its lower electrical resistivity and superior electromigration properties. Electrodeposition as a copper metallization strategy has been shown to offer significant advantages in terms of cost and ease of handling over other currently used metallization techniques such as evaporation, sputtering or chemical vapor deposition. A major advantage is that electrodeposition is a wet process and does not require vacuum conditions. Typically, a lithographic process is used to localize the copper deposit on the semiconductor surface, determined by the selective removal of a photoresist exposed to illumination through a patterned mask. Other approaches for metal patterning of surfaces have been explored involving scanning tunneling microscopy, imprint technologies or resistless patterning using photoelectrodeposition, ion-bombardment or localized thermal plating. However, in general, such approaches are only applicable to wiring on extremely flat and contiguous surfaces and usually require some type of contact or near contact with the semiconductor surface.
Copending U.S. patent application Ser. No. 09/061,818 described a novel technology which allows for the formation of electrical connections between isolated metal components. The method is based on the coupled electrodissolution and electrodeposition between two components in line with an electric field and is referred to as spatially coupled bipolar electrochemistry (sometimes hereinafter referred to as xe2x80x9cSCBExe2x80x9d). A particular advantage of the method is that distances comparable in scale to the components involved can be spanned. This is in sharp contrast with conventional electrodeposition metallization strategies of semiconductors, which are limited either to the creation of thin films or the filling of templates.
The present invention is a novel extension of the technology of U.S. patent application Ser. No. 09/061,818 into making more devices not only in three dimensions using toposelective SCBE, but also into using the process for making electric current rectifying devices (diodes) by controlling the parameters of the SCBE process in a manner never thought of before. It was surprising that diodes would be formed using this process.
One aspect of the present invention relates to a process of making an electric current rectifying device using spatially coupled bipolar electrochemical deposition comprising: (a) placing a source of electrically conductive material and at least two electrically conductive substrates and at least one semiconductor into an environment capable of conducting electricity and containing electrodes; (b) aligning the substrates and the semiconductor with respect to the electrodes such that the electrodes are not in contact with the substrates or the semiconductor and such that the material will form a conductive structure between and in contact with the substrates and the semiconductor when an electric field is applied between the electrodes; (c) applying a voltage to the electrodes to create a first electric field of a sufficient strength between the electrodes and for a time sufficient to form a first electrically conductive structure between and in contact with a first of the substrates and the semiconductor, the electrically conductive structure being substantially aligned with the first electric field; (d) reversing the polarity of the voltage applied to create a second electric field of a sufficient strength between the electrodes and for a time sufficient to form a second electrically conductive structure between and in contact with a second of the substrates and the semiconductor, the electrically conductive structure being substantially aligned with the second electric field; the semiconductor thus being transformed into the rectifying device.
Another aspect of the present invention relates to a process of making an electric current rectifying device using spatially coupled bipolar electrochemical deposition comprising: (a) placing at least two electrically conductive substrates comprising sources of electrically conductive material and at least one semiconductor into an environment capable of conducting electricity and containing electrodes; (b) aligning the substrates and the semiconductor with respect to the electrodes such that the electrodes are not in contact with the substrates or the semiconductor and such that the material will form a conductive structure between and in contact with the substrates and the semiconductor when an electric field is applied between the electrodes; (c) applying a voltage to the electrodes to create a first electric field of a sufficient strength between the electrodes and for a time sufficient to form a first electrically conductive structure between and in contact with a first of the substrates and the semiconductor, the electrically conductive structure being substantially aligned with the first electric field; (d) reversing the polarity of the voltage applied to create a second electric field of a sufficient strength between the electrodes and for a time sufficient to form a second electrically conductive structure between and in contact with a second of the substrates and the semiconductor, the electrically conductive structure being substantially aligned with the second electric field; the semiconductor thus being transformed into the rectifying device.